Braided endoluminal device having tapered filaments

ABSTRACT

A stent comprising a plurality of continuous filaments braided together, at least one filament comprising a tapered filament having at least one first region having a first, relatively-larger cross-sectional area and at least one second region having a second, relatively-smaller cross-sectional area. The stent itself may have a tapered diameter, such as from one end to the other. A method for treating a lumen with the stent is also claimed

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 10/750,131,filed Dec. 31, 2003, which is a continuation of application Ser. No.09/949,586, filed Sep. 10, 2001 (issued as U.S. Pat. No. 6,685,738 onFeb. 3, 2004), which is a continuation of application Ser. No.09/494,980, filed Jan. 31, 2000 (issued as U.S. Pat. No. 6,325,822 onDec. 4, 2001); this application is also related to U.S. patentapplication Ser. No. 09/494,704, entitled “BRAIDED BRANCHING STENT,METHOD FOR TREATING A LUMEN THEREWITH, AND PROCESS FOR MANUFACTURETHEREOF” by Chouinard, Haverkost, and Peiffer, and filed on Jan. 31,2000 (issued as U.S. Pat. No. 6,398,807 on Jun. 4, 2002).

TECHNICAL FIELD

This invention relates generally to endoluminal stents, grafts, and/orprostheses and, more specifically, to braided stents adapted fordeployment in branched lumina and processes for their manufacture.

BACKGROUND OF THE INVENTION

A stent is an elongated device used to support an intraluminal wall. Inthe case of a stenosis, a stent provides an unobstructed conduit forblood in the area of the stenosis. Such a stent may also have aprosthetic graft layer of fabric or covering lining the inside oroutside thereof, such a covered stent being commonly referred to in theart as an intraluminal prosthesis, an endoluminal or endovascular graft(EVG), or a stent-graft.

A prosthesis may be used, for example, to treat a vascular aneurysm byremoving the pressure on a weakened part of an artery so as to reducethe risk of rupture. Typically, a prosthesis is implanted in a bloodvessel at the site of a stenosis or aneurysm endoluminally, i.e. byso-called “minimally invasive techniques” in which the prosthesis,restrained in a radially compressed configuration by a sheath orcatheter, is delivered by a deployment system or “introducer” to thesite where it is required. The introducer may enter the body through thepatient's skin, or by a “cut down” technique in which the entry bloodvessel is exposed by minor surgical means. When the introducer has beenthreaded into the body lumen to the prosthesis deployment location, theintroducer is manipulated to cause the prosthesis to be ejected from thesurrounding sheath or catheter in which it is restrained (oralternatively the surrounding sheath or catheter is retracted from theprosthesis), whereupon the prosthesis expands to a predetermineddiameter at the deployment location, and the introducer is withdrawn.Stent expansion may be effected by spring elasticity, balloon expansion,or by the self-expansion of a thermally or stress-induced return of amemory material to a pre-conditioned expanded configuration.

Various types of stent architectures are known in the art, includingmany designs comprising a filament or number of filaments, such as awire or wires, wound or braided into a particular configuration.Included among these wire stent configurations are braided stents, suchas is described in U.S. Pat. No. 4,655,771 to Hans I. Wallsten andincorporated herein by reference, the '771 Wallsten patent being onlyone example of many variations of braided stents known in the art andthus not intended as a limitation of the invention described hereinlater. Braided stents tend to be very flexible, having the ability to beplaced in tortuous anatomy and still maintain patency. The flexibilityof braided stents make them particularly well-suited for treatinganeurysms in the aorta, where the lumen of the vessel often becomescontorted and irregular both before and after placement of the stent. Asnoted in the '771 application, devices having braided architecture “mayalso be designed to act as a filter for thrombosis, for example byapplication in Vena Cava Interior to prevent the formation of lungemboliae.” The '771 application further includes as FIG. 8 to thatapplication (reproduced as FIG. 18 in this application), a vena cavafilter which is described in that application as follows (with the term“FIG. 18” substituted for “FIG. 8” in the original text, and elements“853” and “854” substituted for “53” and “54,” respectively to avoidduplication of element number within this specification):

-   -   In [FIG. 18] there is shown a modified embodiment of the        flexible tubular body. In this embodiment the body consists of a        cylindrical circular part [853] which at one end thereof changes        to a diminishing part or end [854] also built up from thread        elements. This device has been found to be suitable for use as a        sieve or filter to prevent thrombosis. The device shown in [FIG.        18] can be applied at the desired location within a blood        vessel, for example Vena Cava Inferior, for the purpose of        preventing lung emboly. Previously known filter means intended        for application within blood vessels for the purpose of catching        thrombosis are associated with the disadvantage that they are        permanently attached in the blood vessel by pointed ends or        latches or the like, positional correction or removal of the        filter not being possible. An example of such device is        described in U.S. Pat. No. 3,540,413. The device according to        the present invention can be inserted into the Vena Cava with        great precision and it does not involve any risk for damages on        surrounding vascular walls which is the case with known devices        used today in surgery for the same purposes.

Among the many applications for stent-grafts is for deployment inbifurcated lumen, such as for repair of abdominal aortic aneurysms(AAA). Various stent-graft configurations are known in the art forbifurcated applications, including single-piece and modular designs,graft designs fully supported by stents, and graft designs onlypartially supported by stents. Referring now to FIGS. 1A and 1B, thereare shown the components of a modular, non-braided, bifurcated, stent 10for use with a fully-supported graft as is fully described in U.S. Pat.No. 5,609,627 to Goicoechea et al and adapted for implantation withinthe aorta of a human. By “fully-supported” it is meant that the graft isadapted to have stent structure underlying the graft throughout theentire length of the graft, as opposed to having extensive lengths ofunsupported graft between anchoring stent portions, as will be describedherein later.

As shown in FIG. 1A, stent 10 comprises a main body 12 which bifurcatesinto a first frustoconical leg transition 14 with a dependent first leg16, and a second frustoconical leg transition 18. Second leg 20 is amodular component comprising a frustoconical part 22 adapted tointerlock within second leg transition 18, and a depending portion 24.Frustoconical part 22 may have barbs 23 to help firmly connect secondleg 20 to leg transition 18. As shown in FIG. 2, such a bifurcated stent10 is typically implanted within the vasculature such that the main body12 and leg transitions 14 and 18 are positioned within the aorta mainportion 26 and with the dependent first leg 16 and depending portion 24of second leg 20 each positioned within respective iliac arteries 28 and30. Modular designs are also available wherein both legs are modularcomponents. All of the bifurcated stents described herein, regardless ofunderlying structure, generally resemble the configuration shown in FIG.2 when fully implanted.

As shown in FIGS. 1A and 1B and as fully described in the '627 patent,the structure of stent 10 is a continuous wire zig-zag structurecomprising a series of struts 32 joined at apices 34 and wound intohoops 36, with abutting hoops joined together in some manner, such aswith sutures, at abutting apices. One potential disadvantage of zig-zagstent architecture is that the apices of the zig-zag structure can rubagainst the graft, causing wear in the graft.

Modular, fully-supported, bifurcated stent-graft designs using braidedarchitecture are also known. Such designs typically comprise a tubularstent that is crimped or pinched together in the middle or at one end toform a septum and two smaller lumina. These two lumina can then be usedas sockets for the iliac sections. The braided stents have the advantageof being very adaptable to tortuous anatomy as compared to other stentarchitectures. The formation of the crimp, however, can cause metalcold-work and embrittlement in the stent wires and can result inbulkiness in the bifurcation region, requiring a relatively largerdeployment profile than other designs.

To overcome the potential disadvantages of modular designs, it is alsoknown to provide one-piece or “unitary” stent designs. Such knowndesigns may be fully supported or only partially supported, such as byhaving anchoring stent portions only located at the end sectionsadjacent each opening of the graft. One piece stent designs having azig-zag stent architecture still have the same disadvantage of potentialgraft wear due to rubbing of the apices. One-piece graft designs thatare only partially supported have the potential disadvantage that thedifferences in radial strength and flexibility between the unsupportedand supported regions makes the stent-grafts susceptible to kinking whennavigating through tortuous lumina.

Thus, there is still a need in the art to provide afully-stent-supported, bifurcated stent-graft that is flexible fornavigation through tortuous lumina and that minimizes the risk ofelements of the stent architecture creating wear in the graft coveringor liner.

SUMMARY OF THE INVENTION

The invention comprises a branching stent for deployment in a lumen, thestent comprising a body that branches into a plurality of legs. At leasta first leg portion of each leg comprises a discrete plurality ofcontinuous filaments braided together and at least a first body portionof the body comprises at least one (preferably more, and more preferablyall) of the continuous filaments from each discrete plurality ofcontinuous filaments braided together. At least one of the legs or thebody may further comprise a second portion thereof having a non-braidedstent architecture, or each of the legs and the body may furthercomprise a braided stent architecture throughout the entire respectivelengths thereof. The stent may be a bifurcated stent having an interfacebetween the body and the legs with an open crotch region between thelegs at the interface or a closed crotch region between the legs at theinterface. A stent with a closed crotch may further comprise an open hipregion.

The invention also comprises a stent for deployment in a lumen, thestent comprising a plurality of continuous filaments braided together,at least one filament comprising a tapered filament having at least onefirst region having a first, relatively-larger cross-sectional area andat least one second region having a second, relatively-smallercross-sectional area. A braided stent having tapered wire according tothe present invention may be a bifurcated stent or a non-bifurcatedstent.

The invention also comprises a method for treating a diseased branchedlumen of a human being, the branched lumen comprising a main sectionthat branches into a plurality of branches. The method comprises thestep of deploying within the branched lumen a branching stent comprisinga body that branches into a plurality of legs. At least a first legportion of each leg comprises a discrete plurality of continuousfilaments braided together, and at least a first body portion of thebody comprises at least one of the continuous filaments from eachdiscrete plurality of continuous filaments braided together. Thedeployment step comprises deploying the body in the main section anddeploying each leg within one of the branches.

The invention further comprises a process for constructing a braided,branched stent having a body and a plurality of legs, each legcomprising a discrete plurality of filaments, the process comprising thesteps of: (a) braiding each plurality of filaments to individually format least first leg portions of each of the legs; and (b) braiding atleast one filament from each plurality of continuous filaments togetherto form a first body portion of the body. Step (a) may comprise thesteps of: (i) braiding a first discrete plurality of filaments to formthe first leg; and (ii) braiding a second discrete plurality offilaments to form the second leg, and step (b) may comprise braiding thefirst plurality of filaments and the second plurality of filamentstogether to form the body. Step (a) may be performed prior to step (b),or vice versa. The stent may be braided around a mandrel having amandrel body, a first detachable mandrel leg, and a second detachablemandrel leg. In such case, step (a)(i) comprises braiding the firstplurality of filaments about the first detachable mandrel leg, step(a)(ii) comprises braiding the second plurality of filaments about thesecond detachable mandrel leg, and step (b) comprises braiding the firstplurality of filaments and second plurality of filaments together aboutthe mandrel body.

The braiding may be performed on a braiding machine having apredetermined plurality of bobbin carriers adapted to revolve in apattern about a longitudinal axis. A first set of bobbin carriers may beadapted to revolve in a first circumferential direction and a second setof bobbin carriers may be adapted to revolve in a second circumferentialdirection, each bobbin carrier adapted to carry at least one bobbin.Each bobbin is adapted to provide one or more filaments for braidingwithin the stent. In such case, step (a)(i) comprises using filamentsfrom a first portion of the predetermined plurality of bobbins to braidthe first leg about the first detachable mandrel leg positionedsubstantially along the longitudinal axis in a braiding zone. Thebraiding zone is defined as a conical zone defined by the filamentsextending from the bobbins to the stent on the mandrel. In step (a)(ii),the process comprises using filaments from a second portion of thepredetermined plurality of bobbins to braid the second leg about thesecond detachable mandrel leg positioned in the braiding zone. Step (b)comprises using filaments from both portions of the predeterminedplurality of bobbins to braid the body about the mandrel body positionedin the braiding zone.

Thus, the process may further comprise the steps of: (A) firstperforming step (a)(i); (B) then removing the first portion of thepredetermined plurality of bobbins from the braiding machine andremoving the first mandrel leg from the braiding zone; (C) thenperforming step (a)(ii); (D) then returning the first portion of thepredetermined plurality of bobbins to the braiding machine, attachingthe first mandrel leg and the second mandrel leg to the mandrel body,and positioning the mandrel body in the braiding zone; and (E) thenperforming step (b). The process may instead comprise the reverse: (A)first performing step (b); (B) then removing the second portion of thepredetermined plurality of bobbins from the braiding machine andattaching the first mandrel leg to the mandrel body; (C) then performingstep (a)(i); (D) then returning the second portion of the predeterminedplurality of bobbins to the braiding machine and removing the firstportion of the predetermined plurality of bobbins from the braidingmachine, attaching the second mandrel leg to the mandrel body, detachingthe first mandrel leg from the mandrel body, and positioning the firstleg of the stent outside the braiding zone so that the first leg doesnot interfere with performance of step (a)(ii); and (E) then performingstep (a)(ii).

BRIEF DESCRIPTION OF DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, some of the features of the drawingare not to scale. On the contrary, the dimensions of some of thefeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following figures:

FIG. 1A is a front view of one stent component of an exemplarybifurcated intraluminal stent known in the art.

FIG. 1B is a front view of a mating stent component adapted to beconnected to the bifurcated stent component of FIG. 1A.

FIG. 2 is a front view of the stent components shown in FIG. 1A and FIG.1B in an assembled configuration implanted in the aortic region of ahuman, as is known in the art.

FIG. 3 is a front view of a portion of an exemplary stent embodimenthaving an open crotch according to the present invention.

FIG. 4A is a front view of an exemplary assembled modular mandrel inaccordance with this invention.

FIG. 4B is a right side view of the assembled modular mandrel of FIG.4A, showing hidden components (not shown in FIG. 4A) with dashed lines.

FIG. 4C is a bottom view of the trunk mandrel portion of the mandrel ofFIG. 4A.

FIG. 5A is a front view of the notch gears of a braiding machine, loadedwith the first set of wire bobbins to form the first leg section of thebraided stent about the first leg mandrel.

FIG. 5B is a front view of the notch gears in the braiding machine ofFIG. 5A, with the first set of bobbins regrouped to the right side afterforming the first leg section.

FIG. 5C is a front view of the notch gears in the braiding machine ofFIG. 5A, with the second set of bobbins regrouped to the left side afterforming the second leg section of the stent about the second legmandrel.

FIG. 5D is a front view of the notch gears in the braiding machine ofFIG. 5C, shown fully loaded with both the first set and second set ofbobbins and both leg mandrels.

FIG. 5E is a front view of the notch gears in the braiding machine ofFIG. 5D forming the braided trunk portion of the stent about the trunkmandrel that is connected to both leg mandrels.

FIG. 5F is a front view of the notch gears in the braiding machine ofFIG. 5A in an alternative embodiment wherein the second set of bobbinsis not regrouped to the left side prior to adding back in the first setof bobbins.

FIG. 6 is a side view of the notch gears in the braiding machine of FIG.5A showing the conical configuration of the wires being braided aboutthe mandrel.

FIG. 7 is a top view of a portion of the notch gears in the braidingmachine of FIG. 5A and a front view of a rack for holding bobbinsremoved from the machine.

FIG. 8 is a front view of a portion of an exemplary stent embodimenthaving a closed crotch and open hips according to the present invention.

FIG. 9 is a front view illustration of an exemplary stent embodimenthaving legs in a 1:1 single filament braiding ratio and the body in a1:1 paired filament braiding ratio according to the present invention.

FIG. 10A is a front view illustration of a portion of an exemplary stentembodiment having a closed crotch and closed hips according to thepresent invention.

FIG. 10B is a front view of an enlarged portion of the stent of FIG.10A, showing interlocked filaments from each leg providing closure forthe crotch.

FIG. 11A is a front view illustration of a portion of another exemplarystent embodiment having a closed crotch and closed hips according to thepresent invention.

FIG. 11B is a front view of an enlarged portion of the exemplary stentof FIG. 11A, showing a staple providing closure for the crotch.

FIG. 12 depicts an end portion of an exemplary stent embodiment havingan atraumatic end winding, the stent having been cut longitudinally andflattened.

FIG. 13A depicts an end portion of an exemplary stent embodiment havingcontinuous apices at the end of the stent as is known in the art, thestent having been cut longitudinally and flattened.

FIG. 13B depicts an end portion of an exemplary stent embodiment havingends that terminate freely at the end of the stent as is known in theart, the stent having been cut longitudinally and flattened.

FIG. 13C depicts an end portion of an exemplary stent embodiment havingends that terminate in a twisted configuration at the end of the stentas is known in the art, the stent having been cut longitudinally andflattened.

FIG. 13D depicts an end portion of an exemplary stent embodiment havingends that terminate in a non-braided configuration with continuousapices at the end of the stent, the stent having been cut longitudinallyand flattened.

FIG. 14A depicts an exemplary side view of a male quick connectcomponent that facilitates removal and replacement of the bobbin carrierin performing the method according to the present invention.

FIG. 14B depicts an exemplary plan view of a female quick connectcomponent that facilitates removal and replacement of the bobbin carrierin performing the method according to the present invention.

FIG. 15A depicts a portion of an exemplary stent embodiment having a 1:1single filament braiding ratio as is known in the art, the stent havingbeen cut longitudinally and flattened.

FIG. 15B depicts a portion of an exemplary stent embodiment having a 2:2single filament braiding ratio as is known in the art, the stent havingbeen cut longitudinally and flattened.

FIG. 15C depicts a portion of an exemplary stent embodiment having a 1:1paired filament braiding ratio as is known in the art, the stent havingbeen cut longitudinally and flattened.

FIG. 16 is a front view of the notch gears of a braiding machine, loadedwith a set of wire bobbins in 1:1-in-train configuration that produces a1:1 paired filament braiding ratio, as is known in the art.

FIG. 17 is a cross-sectional view of an exemplary stent according to thepresent invention comprising tapered filaments.

FIG. 18 is a reproduction of FIG. 8 from U.S. Pat. No. 4,655,771,showing a braided tubular body used as a combined graft and filter.

DETAILED DESCRIPTION OF INVENTION

The invention will next be illustrated with reference to the figureswherein similar numbers indicate the same elements in all figures. Suchfigures are intended to be illustrative rather than limiting and areincluded herewith to facilitate the explanation of the apparatus of thepresent invention.

Referring now to FIG. 3, there is shown a bifurcated, braided stent 50according to the present invention. As shown in FIG. 3, the stentcomprises a trunk section 52, a first iliac leg 54 and a second iliacleg 56. Stent 50 as shown in FIG. 3 is a unitary stent. That is, iliaclegs 54 and 56 are continuous with trunk section 52, unlike modularstent designs in which two or more stent segments are assembled togetherto form the various parts of the stent (e.g., the trunk section and thetwo legs). As used herein, the term “unitary” means a stent havingportions of each of its various parts made as a single unit. Thus, aunitary stent contemplates a stent whose entire length of all of itsparts are made as a single unit, without the need to attach additionalstent segments upon deployment. In addition, a unitary stent may be usedin conjunction with stent segments, if it is desired to attach suchsegments to either the legs or the trunk section upon deployment.

It should be noted herein that unitary stent 50 as shown in FIG. 3 ismerely one exemplary embodiment, and that this invention is applicableto “modular”, braided stents as well. As used herein, the term “modular”means a stent having at least two discrete portions adapted for assemblyin situ. As is well-known in the art, one type of exemplary modularbifurcated stent may include a trunk section that bifurcates into asingle leg on one side adapted to extend into one iliac, and a socket onthe other side, with the other leg being a modular piece adapted to beinserted into the socket, similar to the configuration shown in FIGS. 1Aand 1B. Another type of modular bifurcated stent may comprise only atrunk section with a bifurcated region that terminates is two shortsockets into which two discrete leg members are adapted to be inserted.Although not depicted herein, such general configurations are well-knownin the art, and when fully assembled, resemble the unitaryconfigurations depicted in FIGS. 3 and 8, except that there is anoverlap region where each leg member is inserted into each socket as iswell-known in the art. The term “leg” as used herein with respect to astent having a body portion and leg portions may refer to a full,integral leg adapted to, for example, extending into an iliac artery, ormay refer to a socket portion of a leg adapted to receive a modular legelement. Thus, although the invention as illustrated and describedherein primarily references full leg structures, each of the methods andstructures described herein is equally applicable to partial legstructures such as sockets for receiving modular leg elements.

Bifurcated region 53 as shown in FIG. 3, rather than being a crimped orpinched region, is formed by the weave of the stent filaments 58R and58L. As can be seen in FIG. 3, a typical braided stent comprises a firstset of filaments 58L wound in a first helical direction (to the left asshown in FIG. 3) and a second set of filaments 58R wound in a second,opposite helical direction (to the right as shown in FIG. 3), forming aplurality of overlaps 55. Filaments 58L and 58R may be wire, such asnitinol or stainless steel, or may comprise polymer or any type offilaments known in the art.

As used herein, a “braided” stent refers to a stent formed of at leasttwo continuous filaments which are interwoven in a pattern, thus formingoverlaps 55, as shown in FIG. 3. At each overlap, one filament ispositioned radially outward relative to the other filament. Followingeach filament along its helical path through a series of consecutiveoverlaps, that filament may, for example be in the radial inwardposition in one overlap and in the radial outward position in a nextoverlap, or may in the inward position for two overlaps and in theoutward position for the next two, and so on. As mentioned above,exemplary braided stents are disclosed in U.S. Pat. No. 4,655,771 toHans I. Wallsten. A typical braided stent is formed on a mandrel by abraiding or plaiting machine, such as a standard braiding machine knownin the art and manufactured by Rotek of Ormond Beach, Fla. Any suchbraiding or plaiting machine may be used, however, and the use ofterminology specific to components of the machine manufactured by Rotekis not intended as a limitation to the use of that machine design. Tothe extent that the terminology used herein is specific to thecomponents of any one or several machines, it should be understood suchcomponents specifically referred to herein generally have correspondingfunctionally equivalent components with respect to other machines. Thus,the scope of the method described and claimed herein for braiding thestent of present invention is not intended to be limited to the specificmachine embodiment described herein, but extends to functionallyequivalent machines also.

Braiding machines can be used for manufacturing the stent of the presentinvention about an exemplary modular mandrel as shown in FIGS. 4A-C.Modular mandrel 60 as shown from the front in FIG. 4A and from the sidein FIG. 4B, comprises a large diameter trunk section 62 and two, smallerdiameter leg sections 64L and 64R. Leg sections 64 may comprise a maleconnector 66, as shown in FIG. 4B, which mates with a female receptacle67 in trunk section 62 as shown in FIGS. 4B and 4C. Hidden lines are notshown in FIG. 4A. Conversely, the female receptacle may be on legsections 64L and 64R and the male connector on trunk section 62.Connector 66 and receptacle 68 may be threaded, may comprise slipfittings, or may otherwise enable leg sections 64L and 64R to bereleasably connected trunk section 62. Tapered recess 69 serves to modelthe stent gradually to the different diameters of an aorta and iliacarteries.

Referring now to FIGS. 5A-F, braiding machine 70 is shown schematicallyas typically comprising a number of notch gears 72 arranged in a circle.Machine 70 shown in FIGS. 5A-F has twenty such notch gears 72, eachnotch gear adapted to rotate in the opposite direction as itsneighboring notch gears, as illustrated by arrows A and B. Thiscounter-rotation passes bobbin carriers 71, and the bobbins 74 mountedthereon, in a sinusoidal fashion from gear to gear, thus causing thebobbins to revolve about a longitudinal axis on which the circle iscentered. The configuration of the notch gears, bobbin carriers, andbobbins to achieve this movement are well-known in the art, and anexample of such a configuration is found in the braiding machinemanufactured by Rotek.

Each bobbin comprises wire 75 wound thereon. The bobbin carrier andbobbin typically interface in a way that helps keep the wire unravelingfrom the bobbin under proper tension, as is known in the art. Althoughthe motion of the bobbins is described herein, it should be understoodthat the bobbins 74 are moved by virtue of being mounted on bobbincarriers 71. Thus, although empty bobbin carriers 71 are shown in FIG.5A, for example, each bobbin 74 also is mounted upon a bobbin carrier,creating a “loaded” bobbin carrier. To reduce clutter in FIGS. 5A-5F,the underlying bobbin carrier is not shown for carriers loaded withbobbins 74. Bobbins 74L, shown in FIG. 5A with wire 75 unraveling fromthe left-hand side of the bobbin as viewed facing the bobbin from thecenter of the circle of notch gears 72, travel sinusoidally around thecircle of notch gears 72 in a counter-clockwise direction as viewed inFIG. 5A. Conversely, bobbins 74R with wire 75 unraveling from theright-hand side of the bobbin as viewed facing the bobbin from thecenter of the circle of notch gears 72, travel in a clockwise direction.Similarly, bobbin carriers 71L travel counter-clockwise and carriers 71Rtravel clockwise.

The mandrel around which braided stent 50 is formed, such as leg mandrel64R as shown in FIG. 5A, is moved in a controlled manner substantiallyalong a longitudinal axis about which the circle of notch gears 72 iscentered and about which the bobbin carriers 71 revolve. Thus, duringprocessing, wires 75 extend from braiding machine 70 to mandrel 64 in aconical configuration, as shown in FIG. 6. As can be seen from FIG. 6,as two bobbins cross one another, their respective filaments form anoverlap such that the filament from the bobbin on the outer radius 76 isdisposed radially outward (with respect to the axis of the stent beingassembled) relative to the filament from the bobbin on the inner radius78. The space contained within the cone formed by the wires extendingbetween the bobbins and the mandrel and including the space occupied bythe mandrel is referred to herein as the “braiding zone” 90. Althoughthe angles α₁ and α₂ of the wire to the mandrel may be varied asdesired, α₁ and α₂ preferably each comprise an angle of approximately55° when the braiding angle of a braided stent β is approximately 110°.This angle may vary dependent upon the exact radial position of thebobbin relative to the mandrel and whether the wire is on the insideradial position or outside radial position on an overlap. Note, forexample, that when bobbin 74L is positioned radially outwardly withrespect to bobbin 74R on gear 72, angle α₁ is slightly larger than angleα₂. As used herein, the phrase “substantially along the longitudinalaxis” as used with respect to the alignment of the moving mandrel meansthat the mandrel does not have to be perfectly centered in the braidingzone, but merely needs to be aligned close enough to the longitudinalaxis that the angles of the filaments between the mandrel and thebobbins allows the braiding operation to create a functional braidwithout tangling the filaments.

Mandrel leg sections 64L and 64R may therefore each comprise a pullerinterface 68 for attaching a “puller” adapted to pull the mandrel awayfrom the circle of notch gears 72 at a controlled rate as the braid isformed. For example, puller interface 68 may be a drilled and tappedhole 68 in mandrel 64R as shown in FIG. 4B, and the puller may be ametal rod that has a threaded end or slip fitting adapted to be threadedor otherwise locked into the hole. The puller rod may be retracted awayfrom the circle, for example, by a set of counter-rotating caterpillartracks which hold the rod therebetween and move the rod in a controlledmanner. Other types of pullers, methods of attachment of the puller tothe mandrel, and means for moving the puller are also acceptable, andthe invention is in no way limited to the exemplary configurationprovided herein. In alternative machine designs, a “pusher” may beprovided at the opposite end rather than a puller. Any means for axiallymoving the mandrel through braiding zone 90 is acceptable.

The circle of notch gears 72 can be considered to have an outer radius76 (on which bobbins 74R are positioned in FIG. 5A) and an inner radius78 (on which bobbins 74L are positioned in FIG. 5A). In the half-fullconfiguration shown in FIG. 5A, each bobbin 74L crosses over one bobbin74R while on outer radius 76 before returning to inner radius 78 andcrossing under another bobbin 74R. The braid created by such a weave canbe said to have a 1:1 single filament braiding ratio (because eachsingle filament crosses under another single filament, then over one,then under one, and so on). The 1:1 single filament braiding ratio isillustrated in FIG. 15A. During the cross-over step where a bobbin onouter radius 76 crosses over a bobbin on inner radius 78, the differencebetween angle α₁ and α₂ is sufficient to assure that the wires clear oneanother without tangling.

To form a braid around a mandrel, wires 75 extending from bobbins 74 canbe secured to the end of the mandrel in almost any manner, such as bytaping them or tying them, and do not even have to be kept in anyparticular orientation. For example, all the wires may all be taped ortied to a single point on one side of the mandrel. Once the braidingmachine starts, it will stabilize into the proper braid configurationafter only a few circumferential hoops of overlaps 55 (shown in FIG. 3)are formed. The portion between the proper configuration and the end caneither be cut away as scrap or unbraided and then manipulated to form anon-braided end winding, as is discussed herein later. In thealternative, to minimize scrap, the ends of wires 75 may be wound aroundpins (not shown) or otherwise secured to the mandrel in a spacedcircumferential configuration similar to the configuration of bobbins 74in braiding machine 70.

In one method for creating the braided bifurcated structure of thepresent invention, the braiding machine is first loaded as shown in FIG.5A with a first portion 73 of a predetermined number of bobbins 74. Thepredetermined number of bobbins may comprise the maximum capacity of themachine and first portion 73 may, for example, comprise half of thebobbin capacity of the machine. The braiding operation is then performedas described above to form a first leg section of the braided stentaround a first leg mandrel, for example leg mandrel 64R (either 64L or64R may be the first leg mandrel, in which case the other is the secondleg mandrel). After braiding the first leg section about mandrel firstleg section 64R, bobbins 74 of first portion 73 can be regrouped to oneside (the right side as shown in FIG. 5B) of the circle of notch gears72.

The method for moving the bobbins may be by any of a number of ways. Forexample, certain bobbin carriers may comprise closed eyelets throughwhich the wire is threaded, in which case the entire bobbin carrier maybe removed. Other bobbin carriers, such as those manufactured, forexample, by the Wardwell Braiding Machine Company of Central Falls,R.I., comprise open, curled guides resembling a “pigtail” such that thebobbins may be simply unlocked and lifted off of their respective bobbincarriers and the filament readily removed from the guide. It should beunderstood that as referred to herein, removing or replacing “thebobbins” on and off of the machine may comprise removing or replacingthe bobbins only or the bobbins as still attached to the bobbincarriers. Where the entire bobbin carrier is removed, the bobbin carriermay be removed by simply removing any fasteners holding it in place, orto facilitate quicker removal and replacement, a quick-connect fittingcan be used. The quick-connect fitting may comprise any number of meanswell-known in the art for providing an interlocking engagement of oneelement with another, such as a magnetic connection, a twist-and-lockconnection, a spring-loaded ball in channel connection, alever-controlled cam connection, or any connection known in the art. Theconfiguration shown in FIGS. 14A and 14B is provided merely to show oneexample of such a quick-connection device. Any quick connection devicemay be used, however, and the invention is by no means limited to theuse of the configuration shown in FIGS. 14A and 14B.

Exemplary quick disconnect comprises a male component 140 (shown in FIG.14A) attached to bobbin carrier base 142 and a female component 141(shown in FIG. 14B), typically attached to the bobbin carrier footplate(not shown) that rides along the notch gears (not shown) of the braidingmachine (not shown). Male component 140 comprises a cylindrical post 144and a cylindrical pin 145 inserted perpendicular to and through thepost. A helical spring 146 extends about post 144 from pin 145 to bobbincarrier base 142. The bobbin carrier (not shown) typically attaches tomale component 140 on the surface (not shown) of bobbin carrier base 142opposite post 144. Female component 141 comprises a base 148 havingtherein a cavity 147 having an X-shaped entryway 149 adapted to acceptthe post and the pin in one of two orientations. To connect malecomponent 140 to female component 141, post 144 and pin 145 are insertedin cavity 149 and spring 146 is compressed while the male component isturned ⅛ of a full revolution such that the pin is positioned inaccordance with indent 150 shown in dashed outline in FIG. 14B. Thus,the spring 146 biases pin 145 against indent 150 in the cavity wall suchthat the post and pin cannot rotate unless the spring is compressedfurther. The X-shape of the entryway 149 allows male component 140 toeither be inserted and turned to the right or inserted and turned to theleft, depending upon which side of the X the pin is inserted into. Todisconnect the components, then, male component 140 may merely bemanipulated to compress spring 146 and then turned ⅛ of a revolutioneither to the left or the right so that the pin can exit the cavitythrough the X-shaped entryway. In an exemplary construction, base 148 offemale component 141 may comprise a block of metal machined to createcavity 149 and indent 150 and then attached to the bobbin carrierfootplate, such as with screws 151.

The bobbin regrouping process can be essentially understood by comparingFIGS. 5A and 5B. Prior to bobbin regrouping, the bobbins are configuredas shown in FIG. 5A, with pairs of bobbins I, II, III, and IV positionedrelative to one another as shown. To regroup the bobbins, pair IIIremains in place, and the remaining bobbins are moved such that thereare no empty bobbin carriers between pairs of loaded bobbin carriers inthe loaded portion of the circle of notch gears 72, as shown in FIG. 5B.Thus, pairs I, II, and IV move from the positions shown in FIG. 5A tothe positions shown in FIG. 5B.

During the bobbin regrouping steps, it is desirable to preserve theclockwise or counter-clockwise rotation of each bobbin 74. Bobbincarriers 71L can be said to form a first set of bobbin carriers thattraverse the circle of notch gears 72 in the counter-clockwisedirection, whereas bobbin carriers 71R form a second set of bobbincarriers that traverse the circle in the clockwise direction. Thus, itmay be desirable for bobbin 74L that rests on a bobbin carrier 71Lbefore regrouping, to also reside on a bobbin carrier 71L afterregrouping. Where the entire bobbin carrier is removed, it is desirablefor the bobbin carrier to be replaced in a position where it travels inthe same direction as it traveled prior to removal. Thus, for examplewhen braiding with a 1:1 single filament braiding ratio in the legs anda 2:2 single filament braiding ratio (described herein later) in thetrunk, bobbin 74 (or bobbin/bobbin carrier combination) on inner radius78 may need to be switched with the bobbin (or bobbin/bobbin carriercombination) on outer radius 76 for every-alternating pair of bobbins.Thus, for example, for pairs of bobbins I, II, III, and IV shown in FIG.5A, where pair III stays in position and the remaining bobbins areregrouped together, pair III and pair I remain with bobbin 74R on outerradius 76 and bobbin 74L on inner radius 78, whereas pair II and pair IVswitch bobbin 74R to inner radius 78 and bobbin 74L to outer radius 76.The counter rotation of the notch gears means that each notch gear 72having a clockwise-rotating bobbin 74L on outer radius 76 hasneighboring notch gears on either side with the clockwise-rotatingbobbin on inner radius 78. In an alternate embodiment, bobbin carriers71L (and therefore bobbins 74L) may travel clockwise instead ofcounter-clockwise, with carriers 71R and bobbins 74R travellingcounter-clockwise. It may be preferable, however, for the tangent of thewire to the bobbin to be on the same side of the bobbin as on themandrel so that the wire is wound on the same helical direction on themandrel as it was on the bobbin. For example, as shown in FIG. 5A, thewire originating from bobbin 74R is tangent to the left side of both thebobbin and mandrel 64R, and likewise the wire originating from bobbin74L is tangent to the right side of both the bobbin and mandrel.

After regrouping of the bobbins is complete, first portion 73 of thepredetermined number of bobbins 74 is removed and put aside, along withthe completed leg braid still on leg mandrel 64R. Referring now to FIG.7, to facilitate removing (and later replacing) first portion 73 ofbobbins 74, the bobbins (or bobbin carriers) may be stored on a rack 80so that the bobbins maintain the correct orientation and do not gettangled while they are set aside. The rack may take any form, from aconfiguration that mimics the configuration of the circle of notch gears72 to a linear configuration wherein each place for holding a bobbin iseasily identified with a corresponding position in the circle. Forexample, as shown in FIG. 7, the rack may comprise a 10-row by 2-columnarray, columns C₇₆ and C₇₈ corresponding to outer radius 76 and innerradius 78 of machine 70, respectively, and rows R_(i)-R_(x)corresponding to pairs of bobbins i-x on machine 70. Thus, the bobbin onouter radius 76 of pair i is placed on row R_(i), column C₇₆ of rack 80,the bobbin on inner radius 76 of pair x is placed on row R_(x), columnC₇₆, and so on.

A second leg is then braided about leg mandrel 64L with a second portion77 of the predetermined number of bobbins 74 in the same manner as thefirst leg, except this time, after the leg has been braided, the secondportion 77 is regrouped to the opposite side (the left side as shown inFIG. 5C) of the circle of notch gears 72. The first portion 73 ofbobbins has a first discrete plurality of continuous filamentsassociated with it while the second portion 77 has a second discreteplurality of continuous filaments associated with it. Thus, each leg 54and 56 is individually braided and comprises a discrete plurality ofcontinuous filaments, such that each leg consists of filaments that areseparate entities relative to the filaments of the other leg. Aftersecond portion 77 has been regrouped, first portion 73 is returned tothe machine, and leg mandrel 64R and the braid thereon are positionedalongside the second leg mandrel 64L as shown in FIG. 5D. The twomandrels are then attached to trunk section mandrel 62 as shown in FIG.5E. With first portion 73 returned to braiding machine 70, each bobbincarrier on the machine now has a bobbin mounted thereon. The braidingoperation continues, now with all forty bobbins traversing the circle ofnotch gears 72 to create a braid around trunk section mandrel 62.

Although not shown, some of the filaments may be curtailed at theinterface between the legs and the trunk portion, such that the trunkportion might consist of less than all of the filaments from the twoportions 73 and 77. Conversely, the trunk portion may comprise more thanall the filaments from the two portions 73 and 77. It is only necessarythat at least one continuous filament from each discrete plurality ofcontinuous filaments extend into the trunk portion, although it ispreferred that at least half of each do so, and most preferred that allof them do so. Furthermore, portions 73 and 77 as illustrated hereineach comprise half of the total number of bobbins. It may be desirablein certain applications, however, for one leg to have more filaments init than the other, such as if one leg has a greater diameter than theother. In such a case, portions 73 and 77 may be unequal.

Rather than winding a first leg, removing the bobbins, then winding asecond leg, bringing back in the removed bobbins, and then winding thetrunk section all on the same machine, a plurality of machines may beused. For example, a first machine may be used only for winding legsections. After each leg section is wound on the first machine, thebobbins may then be removed such as onto a rack as described above, andported to a section machine. The second machine may be used forcombining together two or more pre-wound leg sections.

A variation on the above method may eliminate the step of regrouping thebobbins to one side of the circle of notch gears 72 before removingfirst portion 73 of the predetermined number of bobbins 74. In suchcase, first portion 73 is merely removed from the circle withoutregrouping, such as in the position shown in FIG. 5A, and stored. Afterbraiding the second leg, second portion 77 of the predetermined numberof bobbins 74 is then left in a spaced configuration similar to thatshown in FIG. 5F, and the first portion 73 is merely inserted to fillthe gaps between the second portion 77. Trunk section mandrel 62 is thenattached to leg mandrels 64L and 64R and the winding continues asdescribed above. This method produces a stent such as is shown in FIG.8.

By either method described above for winding about trunk section mandrel62, the wires are wound in a 2:2 single filament braiding ratio with themachine at full capacity as shown in FIG. 5E. A 2:2 single filamentbraiding ratio is illustrated in FIG. 15B wherein, for example,following consecutive overlaps of single filament 152 wound in a firsthelical direction, the filament travels over two oppositely-woundfilaments 153 and 154 at overlaps 155 and 156, respectively, and thentravels under two filaments 157 and 158 at overlaps 159 and 160,respectively, and so on. This is true of each filament in the braid.FIG. 15A illustrates a 1:1 single filament braiding ratio, whereinfollowing consecutive overlaps of filament 161 wound in a first helicaldirection, the single filament travels over one oppositely-woundfilament 162 at overlap 163 and then travels under filament 164 atoverlap 165, and so on. The stent may be manufactured using braidingmachines having a different number of notch gears or using a differentpercentage of the capacity when winding, thus allowing preparation ofstents having a 1:1 single filament braiding ratio throughout, a 1:1paired filament braiding ratio as shown in FIG. 15C and described below,or other configurations as desired. The exact winding configuration,however, is not intended as a limitation upon this invention.Furthermore, the illustrations in FIGS. 15A-C are intended only todepict the general braiding configurations of the filaments in relationto one another, and do not necessarily represent the actual number offilaments or the precise look of an actual stent.

A 1:1 paired filament braiding ratio can be achieved by positioning thebobbin carriers on the notch gears in such a way that the bobbinstraveling in the same helical direction travel in pairs such that nobobbin traveling in the opposite direction crosses in-between the pairs.This particular bobbin carrier configuration for achieving a 1:1 pairedfilament braiding ratio may also be referred to as “1:1-in-train”configuration, referring to how the bobbin pair travel together as iflinked in a train. Such a positioning is shown in FIG. 16, where bobbins74L proceed about the circle counterclockwise and bobbins 74R proceedclockwise.

Referring now to FIG. 9, this method may be used, for example, toproduce a stent 92 having a body section 52 with a 1:1 paired filamentbraiding ratio. The 1:1 paired filament braiding ratio is also shown inFIG. 15C. As shown in FIG. 15C, following a pair of filaments 166 and167 wound in a first helical direction through consecutive overlaps, thepair travels together over a pair of oppositely-wound filaments 168 and169 at overlap 170 and then travels under another pair ofoppositely-wound filaments 171 and 172 at overlap 173.

In an alternative embodiment for achieving a 1:1 paired filamentbraiding ratio, each bobbin carrier 71 may be adapted to hold twobobbins. The body of the stent may be wound with the bobbins grouped twobobbins to a single carrier, whereas the legs are wound with the bobbinsdistributed with only a single bobbin per each occupied carrier. Thisconfiguration for winding the body appears similar to FIG. 5A or 5F fromabove, except that each bobbin as shown represents two bobbins 74stacked one on top of another. The stacked configuration can be derivedessentially by first grouping the bobbins as shown in FIG. 5D and thenconsolidating, for example, bobbin 74L_(ix) on top of 74L_(x) and bobbin74R_(ix) on top of 74R_(x) and so on around the circle, so that theresulting configuration resembles the configuration in FIG. 5F but withtwo bobbins stacked one on top of the other. The result is that eachcarrier in each set of carriers having a common direction of rotationhaving two bobbins thereon is surrounded on both sides by emptycarriers, such as for example, carrier 74L having empty carriers 71L oneither side as shown in FIG. 5F. Similarly, each pair of loaded carriershaving two bobbins apiece has an empty carrier therebetween, such as forexample, carriers 74R having empty carrier 71R therebetween as shown inFIG. 5F.

The braided bifurcated stent may also be constructed by processes thatare essentially the reverse of those described above. By such processes,the braiding begins about trunk section mandrel 62 with the fullcapacity of bobbins as shown in FIG. 5E, and then one portion of thebobbins 74 are removed from the machine and set aside while one leg ofthe stent is braided about a leg mandrel using the remaining portion ofthe bobbins. For example, first portion 73 may be removed while secondportion 77 forms a braid about mandrel 64L as shown in FIG. 5C. Afterthe trunk section and one leg of the stent have been created with oneportion of the bobbins, that portion is removed and the other portion isreturned to the machine so that the other leg can be braided about theother leg mandrel. Thus, second portion 77 may be removed and firstportion 73 replaced in the machine to form a braid about mandrel 64R asshown in FIG. 5B. Similar to the process wherein the legs are braidedfirst, the full set of bobbins can be split to make the legs such thatall the bobbins on one portion are used for one leg and all the bobbinson the other portion are used for the other leg, such as is shown inFIGS. 5B and 5C, or the bobbins used to braid one side and the bobbinsused to braid the other side may comprise alternating pairs prior tobeing split, such as is shown in FIGS. 5A and 5F. Because one leg mustbe braided first and then the other leg must be braided in a positionparallel to that leg, leg mandrel 64 must be removed and thefirst-created leg bent back out of the path of braiding zone 90 duringcreation of the second-created leg. Similarly, during creation of thefirst-created leg, the set of bobbins 74 and wires 75 connected theretofor creation of the second-created leg and extending from the trunksection of the stent must be pulled into a position that does notinterfere with the braiding of the first-created leg.

Depending on the method of grouping the bobbins when converting frombraiding the legs to braiding the body, or vice versa, crotch region 93of the stent may be open or closed. The method wherein the bobbins aregrouped such that the bobbins from one leg are grouped on one side ofthe machine and the bobbins from the other leg are grouped on the otherside of the machine as shown in FIG. 5D, produces a stent with an opencrotch 93 such as is shown in FIG. 3. An EVG constructed using a braidedstent having an open crotch thus has an unsupported bifurcation septum.That is, the graft may not have underlying stent structure in the areawhere the graft bifurcates into the two legs. This may provide certainadvantages, such as elimination of any graft-stent wear in thatparticular region, which is a region that may be subjected to moremovement than other portions of the stent, and thus likely to providemore such wear in other designs.

The method wherein the bobbins from each leg are alternated with thebobbins from the other leg as described with respect to FIG. 5F,produces a stent with a closed, woven crotch 93 and open hips 95, suchas are shown in FIG. 8. To provide a closed crotch for the design shownin FIG. 3, one or more filaments from the adjacent legs may be crossedin crotch region 93 as illustrated in the enlarged view in FIG. 10B.Other configurations for closing crotch 93 with crossing filaments maybe provided, such as by switching bobbins from one carrier to another asdesired to produce different degrees of interwinding. Referring now toFIGS. 11A and 11B, it may be desirable to group certain of the braidedfilaments 58 together, in particular filaments from opposite legs incrotch region 93, using staples or sutures 96 to provide additionalstructure.

To provide increased radial strength at the ends of the braided stent ofthis invention or to counteract a known end-effect of braided stentarchitecture wherein the ends tend to have lesser radial strength thanthe intermediate portion of the stent, the ends may be flared as is wellknown in the art, or the ends may comprise a non-braided stentarchitecture such as is shown in FIG. 12. The structure and method formaking a hexagonal non-braided architecture 97 with an overlappingzig-zag end winding 98 shown in FIG. 12 is disclosed fully in pendingU.S. patent application Ser. No. 09/442,165 by the common inventorsChouinard and Haverkost of this invention, filed on Nov. 17, 1999,assigned to the common assignee, and incorporated herein by reference.Consistent with the disclosure in the '165 application, a stentaccording to the present invention having a braided crotch region mayhave a non-braided architecture in any portion of the stent other thanin the crotch. For example, in one embodiment every region except thecrotch region may have a non-braided architecture. Other embodiments mayinclude non-braided architecture in any region of the stent whereadditional radial strength is desired, such as between two braidedregions. Yet another embodiment may have a non-braided architecture atevery end on both the distal (furthest from the position outside thelumen from which the stent is introduced) and proximal (nearest to theposition outside the lumen from which the stent is introduced) ends ofthe stent, or on only selected ends of the stent, such as only on theupstream end or ends. The end architecture is not limited to thearchitecture shown and described above, but may comprise any number ofconfigurations known in the art. If desired, a separate stent havinggreater radial strength may be deployed to overlap one or more of theends, as is also known in the art.

Another method for developing a greater radial strength in one sectionof the stent relative to another comprises using a tapered wire to formthe stent. For example, the wire can taper from a first, relativelysmaller diameter or cross-sectional area used for braiding leg sections54 and 56, for example, to a second, relatively larger diameter orcross-sectional area used for braiding body 52. Thus, body 52 may have agreater radial strength than otherwise provided by a single wirediameter throughout. The taper may also be reversed to provide greaterradial strength in the legs, if desired. This tapering may also beapplied to non-bifurcated, braided stent designs. The use of acontinuous wire having regions of different cross-sectional area forproviding variable stiffness in different regions of a stent isgenerally discussed in U.S. application Ser. No. 09/442,192 to Zarbatanyet al., incorporated herein by reference.

Tapered filaments may be used on any braided stent, not just on abifurcated stent. All of the plurality of continuous filaments may betapered filaments, or only a fraction of the filaments. In anon-bifurcated stent, one end portion of the braided stent may comprisethe larger cross-section ends of all the tapered filaments and the otherend portion of the stent may comprise the smaller cross-section ends ofall the tapered filaments. As used herein in connection with the braidedstent, the “end portion” may comprise only a short portion, such as asingle row of overlaps that includes the end of the stent, or mayinclude a larger portion, such as one half or more of the stent thatincludes the end. One example of such a non-bifurcated stent comprisingtapered wire is shown in FIG. 17. Stent 175 comprises a distal endportion 176 and a proximal end portion 177. The distal end portion has alarger stent diameter D1 and the proximal end portion has a smallerstent diameter D2. In certain applications, it may be desirable for thelarger diameter portion of the stent to comprise a larger diameterfilament than the filament diameter in the smaller diameter portion.Thus, as shown, each filament may have a diameter d1 in the largerdiameter portion of the stent and a smaller diameter d2 in the smallerdiameter portion of the stent. Furthermore, both the stent and the wiremay gradually taper, such that intermediate diameters D3 and d3 arepresent in the region between diameters D1 and D2. In other embodiments,the diameter of the wire may taper less gradually, such that the changein wire diameter along the stent is more in the nature of a step-change.In one exemplary embodiment, for example, D1 may equal about 24 mm andD2 may equal about 12 mm, with d1 equal to about 0.355 mm and d2 equalto about 0.255 mm. Any variety of dimensions may be used. In someapplications D1 may equal D2, with only d1 and d2 being varied along thelength of the stent.

The tapered-filament stent may comprise any combination of end windingsor braiding ratios discussed herein or known in the art. Thetapered-filament stent may be configured in any way desired forplacement in a lumen, such as tapering from one end to the other asshown in FIG. 17, or with a smaller diameter in the middle than in theends, or vice versa, or merely a single diameter throughout. All of thewires in the braided stent may be tapered, or only some fraction of thewires. The filament may have multiple tapers, such as from a largerdiameter at one end, to a smaller diameter in the middle, to a largerdiameter at the other end, or vice versa. The smaller diameter sectionof the filament may be positioned such that is coincides with a tortuousportion of a lumen requiring greater flexibility than other regions ofthe stent. Although described herein with reference to a larger orsmaller diameter, the wire may have a non-round cross-section, in whichcase the wire may taper from a relatively larger cross-sectional area toa relatively smaller cross-sectional area.

The end architecture as shown in FIG. 12 can be described as“atraumatic” in the sense that there are no loose wire ends that maypuncture or irritate (cause trauma to) the lumen wall afterimplantation. Other methods of providing atraumatic ends may also beused as are known in the art. In particular, the stent may comprise,rather than, for example, ten filaments wound onto ten bobbins, fivecontinuous filaments each having a first end wound onto a first bobbinand a second end wound onto a second bobbin, thus still having tenbobbins in all. The filaments can be positioned on the braiding machinewith the midpoint of the filament making a loop around, for example, aradially protruding pin secured in the mandrel, and the first and secondbobbins positioned on bobbin carriers in positions consistent with thehelical angle of the stent and the distance of the mandrel from thebobbin carriers. Thus, the first and second bobbins may be positioned atopposite ends of a radius of the circle of notch gears, or at oppositeends of some chord through the circle, depending on the exactconfiguration of the machine and desired helical angle of the stent. Anexemplary process for providing a stent with such ends is described inpublication WO 99/25271 to Burlakov et al. and is incorporated herein byreference.

Thus, using the method described above, one end of the stent hascontinuous-wire apices 99 such as are shown in FIG. 13A at one end. Thefilaments on the opposite ends may be freely terminating ends 100, suchas are shown in FIG. 13B; twisted together ends 101, such as are shownin FIG. 13C and in publication WO 99/25271; or atraumatically disposedends in a non-braided architecture, such as for example in positions 102and 103 as shown in FIG. 12 and further discussed in U.S. patentapplication Ser. No. 09/442,165. These are only examples, however, asthe free ends may terminate in any way known in the art. Although oneend of a stent may have some combination of continuous-wire apices 99and otherwise-terminated free ends 100, 101, or 102 and 103, thepreferred embodiment comprises one end of the stent having onlycontinuous-wire apices 99. It should also be understood that because thewinding process proceeds from one end of the stent to the other,typically either the body end comprises continuous-wire apices 99 andthe leg ends comprise otherwise-terminated free ends 100, 101, or 102and 103, or the leg ends comprise all continuous-wire apices and thebody end comprises all otherwise-terminated free ends. All or only someof the leg ends may comprise continuous-wire apices.

The above method for providing continuous-wire apices at one end mayalso be combined with the use of tapered wire as described herein. Forexample, a wire having multiple tapers with a relatively smallerdiameter in a middle region of the wire and a relatively larger diameterin the opposite end regions, may be wound onto two bobbins. Therelatively smaller diameter wire may be, for example, wound about aprotruding pin at the midpoint of the wire, and the each leg regionbraided as described herein. The trunk region may then be braided asdescribed herein, with the taper in the wire diameter located such thatthe trunk has a relatively larger diameter wire than each of the legs.The wire may comprise only the first diameter at the opposite ends andthe second diameter in the middle, with a gradual taper between regions,or the wire may comprise a third diameter intermediate the end andmiddle diameters for use in the bifurcated region.

The use of continuous-wire apices at one end may be further combinedwith the configurations described in U.S. patent application Ser. No.09/442,165, wherein one or more regions of the stent may comprise anon-braided configuration. Thus, for example, the midpoint of a wire,such as a tapered wire, may be positioned at a non-braided end of astent, creating continuous apices 104 such as are shown in FIG. 13D. Thenon-braided architecture may be created, for example, by winding thewire about pins on a mandrel as is well known in the art, and then oncethe non-braided section has been formed, braiding the remainder of thestent about the mandrel as described herein. The parallel wire sections105 in the non-braided portion may be optionally welded together priorto braiding the remainder of the stent.

The above combinations may also be used with a non-bifurcated, braidedstent. For example, a braided, non-bifurcated stent may comprise taperedfilaments wherein the ends of the stent comprise larger cross-sectionalarea regions of the tapered filaments and the middle of the stentcomprises the smaller cross-sectional area regions of the taperedfilaments. Conversely, the smaller cross-sectional area regions may beon the ends and the larger cross-sectional area in the middle. As thelarger cross-sectional area wire tends to provide greater stiffness orgreater radial strength or both, the larger cross-sectional wire may beused in any region of the stent desired to have increased stiffness andradial strength relative to the rest of the stent, or may be used incertain regions to counteract influences which otherwise would result inlesser stiffness or lesser radial strength in such regions. Atraumaticend windings, such as the continuous-wire apices described herein andwith reference to Publication WO 99/25271 and the various configurationsas described herein with reference to U.S. patent application Ser. No.09/442,165, may also be used in conjunction with tapered filaments insuch braided, non-bifurcated stents. Such end windings may also be usedin non-bifurcated stents without tapered filaments.

To deploy the stent of this invention, the stent is typically compressedinto a radially compressed state into an introducer as is well-known inthe art. The stent is then introduced to the lumen into which it is tobe deployed, navigated through the lumen to a deployment location,typically a diseased artery such as the aorta, and then expanded to aradially expanded state in the deployment location as is known in theart. The deployment of a unitary stent of the present invention is thusdeployed by a method similar to that used for any unitary bifurcatedstent known in the art, and the deployment of a modular stent accordingto the present invention is thus deployed by a method similar to thatused for any modular bifurcated stent known in the art.

Although bifurcated stent designs have been shown and described herein,the method of the present invention may be used for creating a stentthat branches into any number of multiple lumen, so long as there are asufficient number of bobbins available in the braiding machine toprovide an adequate number of wires for braiding the branch sections. Tothe extent that existing braiding machines may not have a sufficientnumber of bobbins, machines with a greater number of bobbins may bedesigned without departing from the scope of this invention.

Although illustrated and described above with reference to certainspecific embodiments, the present invention is nevertheless not intendedto be limited to the details shown. Rather, various modifications may bemade in the details within the scope and range of equivalents of theclaims and without departing from the spirit of the invention.

1. An endoluminal implant comprising a plurality of continuous filamentsbraided together, at least one filament comprising at least one firstregion having a first cross-sectional area and at least one secondregion having a second cross-sectional area, wherein the firstcross-sectional area is larger than the second cross-sectional area. 2.The implant of claim 1, wherein the at least one filament comprises astep-change between the first region and the second region.
 3. Theimplant of claim 1, wherein all of the plurality of continuous filamentscomprise a step-change between each first region and each second region.4. The implant of claim 1, wherein the at least one filament comprises atapered filament.
 5. The implant of claim 1, wherein all of theplurality of continuous filaments comprise tapered filaments.
 6. Theimplant of claim 1, wherein the implant comprises an end havingatraumatic end windings.
 7. The implant of claim 1, wherein the at leastone filament comprises a circular cross-section.
 8. The implant of claim1, wherein the at least one filament comprises a non-roundcross-section.
 9. The implant of claim 1, wherein the implant tapersfrom a first end having a first diameter to a second end having a seconddiameter smaller than the first diameter.
 10. The implant of claim 1,wherein the at least one filament further comprises a third regionhaving a cross-sectional area intermediate the first and secondcross-sectional areas.
 11. The implant of claim 1, wherein a first endof the implant has a first diameter and a second end of the implant hasa second diameter smaller than the first diameter.
 12. The implant ofclaim 11, wherein the implant comprises the first region of the filamenthaving the first cross-sectional area at the first end of the implantand the second region of the filament having the second cross-sectionalarea at the second end of the implant.
 13. The implant of claim 12,wherein the implant e comprises an intermediate portion having a thirddiameter intermediate the first and second diameters, and theintermediate portion comprises a third region of the at least onefilament having a third cross-sectional area intermediate the first andsecond cross-sectional areas.
 14. The implant of claim 1 wherein theimplant comprises a first portion and a second portion, wherein thesecond portion is more flexible than the first portion and comprises thesecond region of the at least one filament having the secondcross-sectional area.
 15. The implant of claim 1 wherein the filamentscomprise wire.
 16. The implant of claim 15 wherein the wire comprisesone of: nitinol or stainless steel.
 17. The implant of claim 1 whereinthe filaments comprise polymeric material.
 18. The implant of claim 1wherein the implant comprises a radially compressed configuration forintroduction into a lumen and a radially expanded configuration fordeployment within the lumen.
 19. The implant of claim 18 wherein theimplant is expandable between the radially compressed configuration andthe radially expanded configuration by one of: balloon expansion,self-expansion via spring elasticity, or self-expansion via a thermallyor stress-induced return of a pre-conditioned memory material.
 20. Theimplant of claim 1 wherein the implant comprises one of: a 1:1 singlefilament braiding ratio, a 2:2 single filament braiding ratio, or a 1:1paired filament braiding ratio.
 21. The implant of claim 1 furthercomprising a body and a plurality of legs, wherein at least a first legportion of each leg comprises a discrete plurality of continuousfilaments braided together and at least a first body portion of the bodycomprises at least one of said continuous filaments from each discreteplurality of continuous filaments braided together.
 22. A method fortreating a human being, the method comprising the step of implantingwithin a lumen of the human being an endoluminal device comprising aplurality of continuous filaments braided together, at least onefilament comprising at least one first region having a firstcross-sectional area and at least one second region having a secondcross-sectional area, wherein the first cross-sectional area is largerthan the second cross-sectional area.
 23. An endoluminal devicecomprising a plurality of continuous filaments braided together, atleast one filament comprising at least one first region having a firstcross-sectional area and at least one second region having a secondcross-sectional area, wherein the first cross-sectional area is largerthan the second cross-sectional area, wherein the endoluminal devicecomprises a radially compressed configuration for introduction into alumen and a radially expanded configuration for implantation within thelumen.
 24. The endoluminal implant according to claim 1, wherein theendoluminal implant comprises a stent.
 25. The endoluminal implantaccording to claim 1, wherein the endoluminal implant comprises aradially compressed configuration for introduction into a lumen and aradially expanded configuration for implantation within the lumen. 26.An endoluminal device comprising a plurality of continuous filamentsbraided together, at least one filament comprising at least one firstregion having a circular first cross-section with a first diameter andat least one second region having a circular second cross-section with asecond diameter, wherein the first cross-section is larger than thesecond cross-section.